The United States could be violating the U.N. Convention Against Torture by force-feeding immigrant detainees on a hunger strike inside an El Paso detention facility, the United Nations human rights office said Thursday.

The Geneva-based Office of the High Commissioner for Human Rights is concerned that force-feeding could constitute “ill treatment” that goes against the convention, which the United States ratified in 1994, spokeswoman Ravina Shamdasani told The Associated Press.

The U.N.’s statement echoes concerns raised by 14 Democratic lawmakers who sent a letter to U.S. Immigration and Customs Enforcement on Thursday requesting more information about nine Indian men who are being force-fed through nasal tubes after refusing to eat to protest what they described as unfair treatment.

One of the hunger strikers, a 22-year-old asylum seeker who has not eaten in more than a month, said he was dragged from his cell three times a day and strapped down on a bed as a group of people poured liquid into tubes inserted into his nose.

“It is critical that ICE commit to ending this practice,” said the letter spearheaded by Texas Democratic Rep. Veronica Escobar, who toured the El Paso Processing Center and met with the men after AP reported on the force-feeding last week.

Hunger strikes are relatively uncommon inside ICE detention. Last month, ICE began non-consensual feeding and hydration of numerous El Paso detainees after a federal judge issued a court order allowing them to be force-fed against their will.

“ICE is committed to preserving the lives of those in its custody and maintaining orderly detention facility operations,” the agency said Thursday in response to the U.N.’s statement. “For their health and safety, ICE closely monitors the food and water intake of those detainees identified as being on a hunger strike. Medical staff constantly monitor detainees to evaluate whether the hunger strike poses a risk to the detainee’s life or permanent health.”

While ICE doesn’t keep statistics on force-feeding throughout the immigration detention system, attorneys, advocates and agency staffers AP spoke with did not recall a situation where it had come to force-feeding. Federal courts have not conclusively decided whether judges must issue orders before ICE force-feeds detainees, so rules vary by district and orders are sometimes filed secretly.

The controversy comes as President Donald Trump prepares to visit El Paso on Monday for his first campaign rally of the year to be held at a coliseum in the bustling border city. The detainees, who are refusing food to protest what they describe as verbal abuse and threats of deportation from guards, are being held in a highly guarded facility surrounded by a chain-link fence on a busy street near the airport.

The U.N. human rights office did not make any recommendation in this case.

The American Medical Association has expressed its concerns about physicians participating in the force-feeding of hunger strikers on multiple occasions, and its own principles of medical ethics state “a patient who has decision-making capacity may accept or refuse any recommended medical intervention.”

The association also endorses the World Medical Association Declaration of Tokyo, which states that when prisoners refuse food and physicians believe they are capable of “rational judgment concerning the consequences of such a voluntary refusal of nourishment, he or she shall not be fed artificially.”